Subnet Calculator
Calculate network, broadcast, host ranges and usable hosts for any CIDR subnet.
Last updated: August 2026
Network
192.168.1.0
Broadcast
192.168.1.255
First host
192.168.1.1
Last host
192.168.1.254
Usable hosts
254
Subnet mask
255.255.255.0
CIDR notation — /24 gives 254 usable hosts, /30 gives 2 (point-to-point links).
How it works
Mask = leading 32−prefix bits set. Network = IP AND mask. Broadcast = network OR ~mask. Usable hosts = 2^(32−prefix) − 2.
Example: 192.168.1.37/24 → network .0, broadcast .255, 254 hosts.
Frequently Asked Questions
What is a subnet mask?
It separates an IP address into the network part and the host part. 255.255.255.0 (/24) keeps the first 24 bits as network and gives 254 usable host addresses.
Why can't I use the first and last addresses?
The first address in a subnet is the network address and the last is the broadcast address — both are reserved and cannot be assigned to devices.
What is CIDR notation?
It writes the network size as a prefix — /24 means 24 bits of network. /24 gives 254 hosts, /30 gives 2 hosts (point-to-point links), /32 is a single address.
How do I choose the right subnet size?
Count your devices, double it for growth, and pick the smallest prefix that fits. A /29 supports 6 usable addresses, a /28 supports 14, and a /24 supports 254.